Naturally occurring substances continue to be an excellent source of new, biologically active compounds. While natural products can present formidable structural problems, X-ray diffraction techniques have proved an expeditious and reliable way to secure structural information. This study proposes the crystallographic examination of a number of unusual natural products that currently possess unknown or insufficiently defined structures. The purpose of this study is to do basic research which may have practical health applications. In addition to structural novelty the compounds in this proposal demonstrated activity in an anticancer assay or pronounced effects on the central nervous system of mammals. Structural information would be required for significant mode of action or synthetic studies. The potentially useful anticancer compounds discussed in detail are the marine substances aplysiatoxin, palytoxin, dictyodial, dictyolactone and an unnamed Dictyota diterpene. The fungal metabolite equisetin and the higher plant metabolite uvarinol will also be examined. Although many nurdles must be passed before these substances would qualify as useful therapeutic agents, they all appear to have elements of structural novelty that are worth pursuing. The CNS active materials are primarily fungal metabolites. They appear to be diterpene-indoles of unusual structure and confusing biogenetic origin. Since they are all elaborated by common spoilage fungi the potential for their entry into the human food chain exits. As structural information is sparse they are characterized by their ability to produce tremors and are called collectively tremorgens.